This invention relates to the field of specification tube cutting machinery and methods used to produce tubes and tubular pieces from longer stock tubes and, more particularly, to an apparatus and method for advancing and cutting a long tube and ejecting the remaining scrap tube from the cutting machine after the last specified piece is cut, thereby increasing the efficiency of the cutting operation and eliminating a time consuming and dangerous work step from the tube cutting process. In particular, the invention provides a gripper for securely holding the tube during the cutting operation. The gripper is attached to a carriage which is horizontally translatable with respect to the cutting apparatus. Additionally, a pusher is provided for automatically ejecting the last piece of cut tubing from the machine. The pusher is mounted on the carriage and reciprocates forward once the last specified piece of tubing has been cut in order to eject the end piece of tubing from the cutting machine. Preferably the tube cutting machine described herein is used in combination with a shear cutting device, although other methods of cutting tubing are known and would be considered operable in the present invention.
Methods for cutting long tubular stock into pieces of specified length are known. For example, in U.S. Pat. No. 2,837,156 to Brehm a conventional machine for cutting continuously advancing tubing is disclosed. This method, known as the Brehm method, is an example of a cutting method that is useful with the invention disclosed herein. In brief, the Brehm method involves the use of two dies, an inner die for contacting the inner surface of the tubing to be cut and an outer die for contacting the outer surface of the tubing to be cut. In order to cut the tubing, one die (generally the outer die) is moved with respect to the other die thereby "shearing" the tubing. This method for cutting tubing is preferred over other prior art methods that involve "sawing" the tubing because very little of the tubing is destroyed. Furthermore, the use of the Brehm method creates tube ends that are generally smooth and burr free.
Over the years, there have been many attempts to improve on the Brehm method in order to improve the quality and efficiency of the cutting process. For example, U.S. Pat. No. 4,205,569 to Horn et al. discloses a tube cutting apparatus using the Brehm method wherein multiple tube segments may be cut in a single shearing operation. After the tubing is cut, the slices of cut tubing are advanced onto an ejector rod that is then retracted to allow the cut tubing to fall into a collection bin. Additionally, the Horn et al. patent discloses dies that define inclined planes in order to cut tubes on a bias.
Similarly, U.S. Pat. No. 5,406,870 to Suitts et al. also discloses an improvement to the basic Brehm method in which the loader and feeder mechanisms for the cutting machine are integrated into one piece of equipment. In particular, in the Suitts et al. patent, a method and apparatus for cutting tubing is disclosed using the shear cutting method wherein the tubing is fed automatically to the cutter and is gripped and advanced to the cutting station. The cut tube is advanced along an arbor and is dropped off into a bin at the end of the arbor. The cutting machine of the Suitts et al. patent is equipped with an infrared sensing system that works in conjunction with computer programming to discard the scrap materials separately from the specification milled tubing without the need for a mechanical stop finger to determine the tube cutoff length.
Thus, while several prior art methods exist for continuously loading and cutting tubing while discarding any scrap created thereby, these methods tend to be complex and expensive, requiring the use of infrared sensing equipment, etc. Additionally, they also require the use of an arbor that extends past the end of the die and various forms of expensive and elaborate equipment add ons.
Accordingly, there exists a need for a method and apparatus for cutting tubing and automatically ejecting any leftover scrap tubing after all of the usable tubing has been cut that is mechanically simple and relatively inexpensive to fabricate and operate and which does not require the use of overly expensive or elaborate equipment to implement.